1. Field of the Invention
The present invention relates to a fan unit and more particularly, though not exclusively, a fan unit including a cooling fan, and an optical apparatus including the fan unit.
2. Description of the Related Art
In optical apparatuses, such as a projector, if a cooling fan is supported by a support member (e.g., a housing), vibration of the fan is transferred to the support member, and therefore, noise is produced. A vibration-dampening structure can facilitate the minimization of the noise. In an operational situation, the noise can provide an irritating environment for audiences during projector use.
Conventionally, some optical apparatuses have a vibration-dampening structure in which rubber cushions are disposed on both sides of the peripheries of mounting holes formed in a fan assembly and the fan assembly is secured between the rubber cushions by screws to reduce the transfer of vibration to a supporting member (refer to, for example, Japanese Patent Laid-Open No. 9-270975, in particular, paragraphs 0010 through 0011 and FIG. 1). Additionally, a vibration-dampening structure has been discussed in which rubber cushions (bushings) are incorporated into a notch formed in a fan assembly and the rubber cushions are secured to a supporting member by screws to reduce the transfer of vibration to the supporting member (refer to, for example, Japanese Patent Laid-Open No. 2000-27799, in particular, paragraphs 0019 through 0029 and FIG. 1). Furthermore, a vibration-dampening structure has been discussed in which a fan assembly includes rubber cushions at its four corners and the fan assembly is supported by a supporting member via the rubber cushions to reduce the transfer of vibration to the supporting member (refer to, for example, Japanese Patent Laid-Open No. 2001-313483, in particular, paragraphs 0018 through 0021 and FIG. 3).
Still furthermore, a vibration-dampening structure has been discussed in which a resilient shaft is disposed in a mounting hole formed in a fan assembly and the resilient shaft is supported by a supporting member to prevent the fan assembly from being in direct contact with the supporting member, thus reducing the transfer of vibration to the supporting member (refer to, for example, Japanese Unexamined Utility Model Registration Application Publication No. 62-34243, in particular, the Claims and FIG. 4).
However, in the vibration-dampening structure discussed in Japanese Patent Laid-Open No. 9-270975, the productivity of assembling the fan unit significantly deteriorates, and therefore, the number of assembling steps and the cost increase. This is because the fan assembly needs to be secured to the supporting member by screws while preventing the rubber cushions from being shifted from the mounting holes formed in the fan assembly. In addition, since the rubber cushions are compressed by the screws, the elastic force of the rubber cushions is reduced. Consequently, the vibration-dampening effect is reduced.
In contrast, the vibration-dampening structure discussed in Japanese Patent Laid-Open No. 2000-27799 has a good productivity of attaching the rubber cushions to the fan unit. However, like the vibration-dampening structure disclosed in Japanese Patent Laid-Open No. 9-270975, since the rubber cushions are compressed by the screws, the elastic force of the rubber cushions is disadvantageously reduced. In the vibration-dampening structure discussed in Japanese Patent Laid-Open No. 2001-313483, the rubber cushions are not compressed by the screws, and therefore, the vibration-dampening effect is not reduced. However, the contact areas between the rubber cushions disposed at the four corners of the fan assembly and the supporting member are large. This results in the easy transfer of the vibration of the fan to the supporting member.
In the vibration-dampening structure discussed in Japanese Unexamined Utility Model Registration Application Publication No. 62-34243, since only the resilient shaft is in contact with the supporting member, the contact area is small. However, since the fan assembly is supported at only one side thereof (i.e., in a cantilever manner), the fan assembly may be tilted due to its own weight. Accordingly, the blow direction of cooling air is unstable, and therefore, it can be difficult to cool a desired location. In the case where the fan assembly is used to, for example, cool a light source lamp of an image projection apparatus, if the desired location is not cooled, the cooling performance decreases, which in turn decreases the luminance of the light source and a projected image.